This invention relates to a thin-film magnetic head with coiled conductors.
A prior art thin-film magnetic head of this type comprises, as shown in FIGS. 1 and 2, a magnetic substrate 1, a spiral pattern conductor layer 2 in the form of a three-turn coil laminated, on the surface of the substrate a non-magnetic insulating layer 3 laminated on the conductive layer 2 and the exposed portion of the magnetic substrate 1, and a magnetic layer 4 laminated on the non-magnetic insulating layer. The thin-film magnetic head of the above structure is arranged to establish a magnetic circuit with a gap A formed on one side of the thin-film magnetic head with which a magnetic recording medium (not shown) comes in contact. Reference numeral 5 designates a terminal conductor layer.
However, this prior art thin-film magnetic head disadvantageously has surfce irregularities in the magnetic layer 4 in correspondence with surfaces irregularities in the conductor layer 2 with the result that the cross-sectional area of the magnetic layer 4 is locally reduced and the consequent magnetic saturation during recording decreases the recording efficiency. One countermeasure for preventing the decrease in recording efficiency may be such that the thickness of the magnetic layer 4 is increased so as to enlarge the equivalent cross-sectional area, but such a countermeasure is not always advantageous. More particularly, it is usual to prepare the magnetic layer 4 by vapor deposition in a vacuum at a temperature of 300.degree. to 350.degree. C. and hence high temperature treatment of the lower layers such as conductor layer 2 and non-magnetic insulating layer 3 is prolonged in proportion to the thickness of the magnetic layer 4. As a result, the resistivity of the conductor layer 2 is liable to increase and the insulative properties of the non-magnetic insulating layer 3 are liable to become degraded. Also, with an increased thickness, internal stress in the magnetic layer 4 is increased, resulting in a tendency for the magnetic layer 4 to peel off. Moreover, when etching the magnetic layer 4 to obtain a desired track width, inclination is increased at the edge and it is difficult to provide a narrow track width with high accuracy.
Another prior art thin-film magnetic head, as shown in FIGS. 3 to 5, comprises laminae of a magnetic substrate 6, a spiral pattern conductor layer 7 in the form of a three-turn coil, a non-magnetic insulating layer 8, a spiral pattern conductor layer 9 in the form of a three-turn coil which is in register with the spiral conductor layer 7, a non-magnetic insulating layer 10, and a magnetic layer 11. The spiral pattern conductor layer 7, insulating layer 8, spiral pattern conductor layer 9, insulating layer 10 and magnetic layer 11 are stacked on the magnetic substrate 6 in this order. The magnetic head of the above structure is arranged to establish a magnetic circuit with a gap B formed on one side of the magnetic head with which a magnetic recording medium (not shown) comes in contact. Reference numeral 12 designate an intermediate terminal conductor layer.
The disadvantages of this thin-film magnetic head are the same as those of the former prior art magnetic head and are aggravated by the following problems. More particularly, as shown in FIG. 5, when the conductor layer 9 crosses the conductor layer 7 across a void between two adjacent turns of the conductor layer 7, a bridge portion of the conductor layer 9 crossing the void sinks and causes unevenness in the conductor layer 9. As a result, a cross-sectional area of the conductor layer 9 is locally reduced at portions 9a and 9b. Consequently, the resistances of the conductor layers 7 and 9 are unbalanced and the allowable current for the conductor layer 9 is appreciably reduced. In addition, the conductor layer 9 is liable to be broken at the portions 9a and 9b.